Action of 3-Hydroxytyramine and some Tryptamine Derivatives on Spinal Neurones

Abstract

PHARMACOLOGICAL studies on the depression of spinal reflexes produced by the topical application of comparatively strong solutions of 3-hydroxytyramine to the exposed spinal cord have led to the conclusion that this catecholamine could be an inhibitory transmitter acting on spinal motoneurones¹. Recently, it has also been suggested that derivatives of tryptamine may be transmitters within the spinal cord². When applied electrophoretically, adrenaline and nor-adrenaline have no action on spinal neurones³ although these catecholamines, 3-hydroxytyramine and many derivatives of tryptamine depress the synaptic excitation of lateral geniculate neurones⁴. These agents are not, however, inhibitory transmitters in this portion of the visual pathway.